The present invention relates generally to underground drilling machines. More particularly, the present invention relates to rod loaders for feeding rods to and from horizontal directional drilling machines.
Utility lines for water, electricity, gas, telephone and cable television are often run underground for reasons of safety and aesthetics. Sometimes, the underground utilities can be buried in a trench that is later back filled. However, trenching can be time consuming and can cause substantial damage to existing structures or roadways. Consequently, alternative techniques such as horizontal directional drilling (HDD) are becoming increasingly more popular.
A typical horizontal directional drilling machine includes a frame on which is mounted a drive mechanism that can be slidably moved along the longitudinal axis of the frame. The drive mechanism is adapted to rotate a drill string (i.e., a length of interconnected rods) about its longitudinal axis. Sliding movement of the drive mechanism along the frame, in concert with the rotation of the drill string, causes the drill string to be longitudinally advanced into or withdrawn from the ground.
In a typical horizontal directional drilling sequence, the horizontal directional drilling machine drills a hole into the ground at an oblique angle with respect to the ground surface. During drilling, drilling fluid can be pumped through the drill string, over a drill head (e.g., a cutting or boring tool) at the end of the drill string, and back up through the hole to remove cuttings and dirt. After the drill head reaches a desired depth, the drill head is then directed along a substantially horizontal path to create a horizontal hole. After the desired length of hole has been drilled, the drill head is then directed upwards to break through the ground surface. A pull-back sequence is then initiated. During the pull-back sequence, a reamer is attached to the drill string, and the drill string is pulled back through the hole. As the drill string is pulled back, the reamer enlarges the hole. It is common to attach a utility line or other conduit to the drill string so that it is dragged through the hole along with the reamer.
A typical horizontal directional drilling machine includes a rod box (i.e., a rack or magazine) for storing rods (i.e., pipes or other elongated members) used to make the drill strings. A rod transfer mechanism is used to transport rods between the drive mechanism of the directional drilling machine and the rod box. During a drilling sequence, the rod transfer mechanism transports rods from the rod box to the drive mechanism. During a pull-back sequence, the rod transfer mechanism transports rods from the drive mechanism back to the rod box.
U.S. Pat. No. 5,607,280 discloses a prior art rod handling device adapted for use with a horizontal directional drilling machine. As shown in FIG. 1, the rod handling device includes a rod box 24 having five vertical columns 41-45. Bottom ends of the columns 41-45 are open so as to define five separate discharge openings 41a-45a through which rods can be fed. A selection member 50 is mounted beneath the discharge openings 41a-45a. The selection member 50 has five pockets 41b-45b, and functions to index or feed rods 20 to and from the rod box 24. For example, during a drilling sequence, the selection member 50 indexes rods 20 from the rod box 24 to a pickup location where the rods are individually picked up and carried to a rotational drive head 16 of the drilling machine by a transfer arm 51. During a pull-back sequence, the transfer arm 51 carries rods 20 from the rotational drive head 16 back to the pickup location, and the selection member 50 indexes the rods from the pickup location back beneath the rod box 24. To move the rods from the selection member 50 back into the rod box, a lift is used to push pipes upwardly into the columns 51-54 of the rod box 24.
During a typical drilling sequence, the rod box is unloaded starting with column 45. After column 45 has been unloaded, column 44 is unloaded. Thereafter, column 43, column 42 and column 41 are sequentially unloaded. During a pull-back sequence (i.e., a sequence in which rods are transferred from the drive head 16 back to the rod box 24), the columns are typically sequentially loaded starting with column 45 and finishing with column 41. Once column 45 has been loaded, a block or plug is manually inserted into pocket 45b of the selection member 50 to prevent additional rods from being loaded into column 45. Thereafter, column 44 is loaded. Once column 44 has been filled, a plug or block is manually inserted into pocket 44b of the selection member 50 to prevent additional rods from being loaded into column 44. Column 43 is then loaded. After column 43 has been loaded, a block or plug is inserted into pocket 43b of the selection member to prevent additional rods from being loaded into column 43, and column 42 is loaded. Once column 42 has been fully loaded, a block or a plug is manually inserted into pocket 42b of the selection member 50 to prevent additional rods from being loaded into column 42, and column 41 is loaded.
One aspect of the present invention relates to a horizontal directional drilling machine including a rod transfer member having a rod retainer that is movable between a first position and a second position. When the rod retainer is in the first position, the rod retainer is adapted to retain a pipe on the transfer member. By contrast, when the rod retainer is in the second position, a rod can be moved from the transfer member without being obstructed by the rod retainer. A sensor is provided for detecting when a pipe is positioned on the pipe transfer member, and for causing the rod retainer to move from the second position to the first position when a rod is detected.
A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed.